Dead Zones Haunt Green Bay as Manure Fuels Algae Blooms
Many gains from the Clean Water Act are lost due to overloads of phosphorous entering waters. Towards the end of the $1.3 billion PCB cleanup in the lower Fox River the environment for fish in Green Bay appeared to be getting worse with major fish die-offs in 2005 and 2013. Oxygen readings showed the average number of oxygen-poor days—defined as levels below 5 milligrams per liter—jumped from 13.5 between 1986 and 1995 to 32.4 for the years between 2007 and 2013.
Die-offs started with gusty winds coming from the south that pushed northward the warm, shallow water of the lower bay. When that water moves north, just like skimming your arm across the surface of a bathtub near the hot water spout to even the tub temperature, it creates a whoosh of cold, oxygen-depleted bottom water headed in the opposite direction.
“How long could you survive with a plastic bag on your head,” a scientist explained. How did that cold water become so oxygen- depleted?
An overload of phosphorus. Once this fertilizing mineral makes its way into a water body, it acts like fuel to a flame, supercharging nuisance algae blooms, which burn up oxygen to create dead zones.
Green Bay and the lower Fox River are suffering from a chronic overdose of phosphorus. There are lots of sources for the nutrient—city sewerage systems, industries, runoff from lawns and streets—but as this chart shows, agriculture is by far the largest contributor.
The state has a plan to put the river and Green Bay on a phosphorus diet under the Clean Water Act. This likely will require expensive pollution-reduction investments for cities and industries, but agriculture runoff remains largely beyond regulation under the Clean Water Act.
Data provided by the state Department of Natural Resources show that phosphorus levels in parts of Green Bay have been, in most years, far beyond what is considered healthy. The target level for the open waters of Lake Michigan is 0.007 milligrams per liter. In recent years, levels 30 times that amount have been detected in the bay.
Yet the old pollution culprits of heavy industry and human sewage are no longer the primary drivers of the problem; the amount of phosphorus pouring from their pipes into Green Bay is just a fraction of what it was four decades ago.
“The Clean Water Act did what it was supposed to do,” says Val Klump, director of the University of Wisconsin-Milwaukee’s Great Lakes WATER Institute. “It cracked down on sewerage districts and industry.”
Klump, who holds a law degree from Georgetown University and a PhD in marine sciences from the University of North Carolina, notes that the Green Bay sewerage district, now known as NEW Water, has gotten so good at taking phosphorus out of its discharges that it is no longer a major factor in the algae blooms. “Even if you take their load down to zero, we still have a problem,” he says.
The papermakers and other industries have made similar improvements in recent decades.
So what is the problem?
Take a look at Wisconsin’s license plate. The answer lies in the farm fields just above the sailboat flying across a blue lake.
This article was adapted by Robert Sijgers, Director, DCEC, from an article by Dan Egan, Milwaukee Journal Sentinel, published Sept. 2, 2021. It was originally published on Sept. 13, 2014 and is a part of the series “A Watershed Moment.” See full article at here.
